1. Field of the Invention
This invention relates to shipping containers for transporting radioactive materials, such as spent fuel rods from nuclear reactors. More particularly, this invention concerns a novel, hermetically sealable cask for transporting radioactive materials as well as novel methods for testing the integrity of the cask seals.
2. Description of the Prior Art
U.S. Pat. No. 3,619,616 describes a container for transporting radioactive materials such as nuclear reactor fuel rods. This container is made up of inner and outer shells with a layer of radiation absorptive material arranged between the shells. The interior of the container is filled with water into which the radioactive material is immersed; and special valve means are provided to accommodate expansion of the water in the container as a result of heating from the radioactive material.
Another type fuel container, which has been used by applicant's assignee, is designed to be purged of all water and to receive and maintain, by means of a hermetic seal, a moisture free gaseous atmosphere such as helium. This latter fuel container does not depend on a special valve to accommodate expansion due to heat since its atmosphere is maintained free of moisture and expansion is thereby held to a minimum.
Other United States patents showing various aspects of containers for radioactive materials are U.S. Pat. Nos. 3,113,215, 3,483,381, 3,770,964 and 3,780,306.